Graphene Backing for Radioisotope Targets

For nuclear physics research, thin film isotopic specialty targets are often requested for the use and in charged-particle-induced experiments. There are also tens of radioisotopes that are of interest for medical imaging, industrial and R&D uses. The targets of interest include B, O, Si, and Cr; isotopes of refractory metals, such as Re, Os, Ir are good examples. However, many of the isotopes cannot be made as free-standing foils and require thin film backing. The limitations of existing backing materials are poor thermal and mechanical stability. Statement of How this Problem or Situation is Being Addressed – All-carbon graphene-based films would be an excellent choice as a backing material due to its high thermal conductivity, high temperature tolerance, low outgassing, mechanical integrity and ease of handling. In addition, it would be possible to electroplate a thin layer of the target material or its precursor over the conducting graphene surface in case of limited availability of the isotope, or if the isotopic material cannot be deposited by sputtering or e-beam or thermal evaporation. For specialty targets, the target material can also be embedded in the graphene matrix during the backing film fabrication. What was done in Phase I - In Phase I, we fabricated thin graphene backing films with B-11, Cr, and Ir targets by different techniques: sputtering deposition, electroplating, and target material embedded in graphene matrix. The fabricated graphene backed targets along with free standing graphene films were delivered to ANL for evaluation. What is planned for Phase II - In Phase II, we will optimize the processes and techniques developed in Phase I, introduce a new target preparation method, fabricate an enriched isotopic Cr-52 target, as well as refractory metal targets (W, Mo, Nb) by different techniques. The fabricated targets will be delivered to ANL for evaluation. Commercial Applications and Other Benefits – The technology that will be developed in this effort may have additional commercial applications in the area of extraction foils for medical cyclotrons, filter membranes, transparent optical conductors, X-Ray and ion beam windows, and polymer nanocomposites for automotive, aerospace and defense applications.